A spoken word consists of a series of movements in the larynx and the mouth, combined with breath. Two closely similar series of such movements may be instances of the same words, though they may also not be, since two words with different meanings may sound alike; but two such series which are not closely similar cannot be instances of the same word. (I am confining myself to one language.) Thus a single spoken word, say “dog,” is a certain set of closely similar series of bodily movements, the set having as many members as there are occasions when the word “dog” is pronounced. The degree of similarity required in order that the occurrence should be an instance of the word “dog” cannot be specified exactly. Some people say “dawg”, and this must certainly be admitted. A German might say “tok”, and then we should begin to be doubtful. In marginal cases, we cannot be sure whether a word has been pronounced or not. A spoken word is a form of bodily behaviour without sharp boundaries, like jumping or hopping or running. Is a man running or walking? In a walking-race the umpire may have great difficulty in deciding. Similarly there may be cases where it cannot be decided whether a man has said “dog” or “dock”. A spoken word is thus at once general and somewhat vague. We usually take for granted the relation between a word spoken and a word heard. “Can you hear what I say?” we ask, and the person addressed says “yes”. This is of course a delusion, a part of the naive realism of our unreflective outlook on the world. We never hear what is said; we hear something having a complicated causal connection with what is said. There is first the purely physical process of sound-waves from the mouth of the speaker to the ear of the hearer, then a complicated process in the ear and nerves, and then an event in the brain, which is related to our hearing of the sound in a manner to be investigated later, but is at any rate simultaneous with our hearing of the sound. This gives the physical causal connection between the word spoken and the word heard. There is, however, also another connection of a more psychological sort. When a man utters a word, he also hears it himself, and so that the word spoken and the word heard become intimately associated for anyone who knows how to speak. And a man who knows how to speak can also utter any word he hears in his own language, so that the association works equally well both ways. It is because of the intimacy of this association that the plain man identifies the word spoken with the word heard, although in fact the two are separated by a wide gulf.